The proposed research is a systematic study of the contributions of stimulus discriminability and proactive interference to registration-retrieval and retention processes in animal memory. The role of these fundamental factors in memory will be analyzed and measured in an integrated series of experiments using four different delayed response and delayed matching paradigms. Effects of drugs (principally scopolamine and d-amphetamine) on the principal behavioral components of memory will be assessed, and results will be related to effects of the drugs in other, non-memory experiments. The research will also examine the effects of drugs and stimulus changes in "attention" in memory. A series of measures of complex behavior (memory, acquisition, and win/stay-lose/shift) is being developed that should provide sensitive indications of the behavioral effects of drugs and toxicants. These measures combine the analyzability and interpretability of discrete trial measures of the complex behavior with the sensitivity of free operant measure of intertrial interval performance. An innovative and flexible system is being developed for control of experiments and analysis of data by a TI 980A minicomputer.